Numerical Simulation Study Of Collision Between Different Diameter Particles And Wall In Industrial Capture Hood

Solid particulate matter is a common pollutant of industrial production.It causes a series of hazards to the indoor environment and occupants'health.Different types of capture hoods are often used to control solid particulate contaminants.As a common research method,numerical simulation technology can quickly and easily predict the migration of particulate matter in the capture hood.Thus the optimum design parameters can be obtained.Because the collision with the wall will change the migration characteristics of the particles and affect its distribution in the capture hood,it becomes an important factor affecting the accuracy of the numerical simulation prediction results.Therefore,a numerical model for particle migration with modified collision boundary conditions should be established,and the difference of the numerical simulation result due to collision effect between particles of different size and wall in industrial capture hood should be clarified,which can improve the accuracy of numerical simulation,and has theoretical significance and engineering application value for the design of the trap hood.Solid particles,which are harmful to human body in industrial production process,usually move at low speed and the particle size is less than 100 microns.Therefore,in order to obtain a particle-wall collision model suitable for the range of particle size and velocity,the applicability of two commonly used models,namely LS-DYNA model and deposition model were analyzed in this paper.SiO₂,the main component of industrial pollutant fly ash,was taken as the research object.A collision model between SiO₂ particles and metal plates of different materials was established in LS-DYNA.The results show that the model is suitable for the case where energy loss is mainly caused by plastic deformation at high incidence speed,the prediction results of the model are quite error while energy loss is mainly caused by intermolecular forces at low incidence speed.Compared with the LS-DYNA model,the deposition model can reflects the collision process between particle and wall accurately when the velocity is less than 20 m/s.Thereafter,based on the deposition model,the low-speed normal collision process between 1-100?m solid particles and wall was numerically calculated.It was found that 1-30?m particles'energy loss was quite different when the incident velocity was smaller than the limit elastic velocity because of the difference of interaction forces between molecules.When the particle size is larger than 30?m,particle size has no significant effect on the energy loss during collision.After that,UDF was compiled according to the deposition model,and the Fluent DPM model was coupled with the deposition model.A numerical model for particle migration with modified collision boundary conditions was established.Then two kinds of capture hood with different structure and trapping mechanism,namely upper suction hood and tube bundle collision hood,are selected as typical examples.The migration of 1-30?m solid particles in the trap hood was numerically simulated and analyzed,and the difference of numerical simulation results of the two types of industrial trap hood under the collision of particles and wall was clarified.The flow field,particle concentration field and capture efficiency of the upper suction hood were analyzed,compared with the numerical calculation model without considering collision effect,when the pollutant emission rate is 0.3m/s,the exhaust velocity is less than 0.6m/s,the capture efficiency simulation results will be 2%-4%higher,when the exhaust velocity is more than 0.6m/s,and the capture efficiency simulation results of the upper suction hood are basically unchanged.When the emission velocity of pollutants is 0.4m/s,the exhaust velocity is less than 0.8m/s,the capture efficiency is 2%-4%higher,when the exhaust velocity is more than 0.8m/s,the simulation results are basically unchanged.The flow field,particle concentration field and particle deposition in the tube bundle collision trap hood were analyzed,it is found that the collision between particles and the wall has a significant impact on the numerical prediction results of the deposition.Among them,the particle size of 1-10 micron has a greater impact.The total deposition of 1-10 micron particles in the trap hood decreases by 5%-10%,while the particles of 20 micron and 30 micron remain basically unchanged.The lower wall is the main collision area,and the deposition deviation is large.The difference of deposition amount of 1-10?m particles on the lower wall is more than 50%,and the difference decreases with the increase of particle size.The computational model presented in this paper lays a foundation for more accurate numerical simulation of the motion law of solid particles with different particle sizes under the impact of wall collision in the future.